While Mr. Hirai’s promotion had been widely expected, many Sony-watchers had expected Mr. Stringer to remain chief executive officer, and a multi-year transition process to unfold. Instead, Mr. Hirai assumes the two main executive slots simultaneously in April. In a brief transition, the 69-year-old Mr. Stringer will remain “executive chairman” until June, and then become the non-executive chairman of the board.

The company’s immediate statements didn’t define in detail just what Mr. Stringer’s role will be going forward, or why the 51-year-old Mr. Hirai was made CEO so quickly. But many of the statements had the tone of a eulogy. “The Board is grateful to Sir Howard Stringer for all he has done…,” Yotaro Kobayashi, the current chairman of the board, said in a statement. “We are also pleased that Sir Howard has accepted our request to remain with Sony after June… ”

Sony officials assembled a long list of Mr. Stringer’s “accomplishments,” starting with the launch of the PlayStation Network business that Mr. Hirai ultimately rode to power, and were preparing to defend Sony’s stubbornly weak financial performance in recent years, a cloud over the Stringer administration. They made the case that Mr. Stringer was on the verge of steering Sony to profitability this fiscal year, which ends March 31, before a series of bad breaks: Japan’s earthquake and tsunami, London riots, the hacking scandal, Thai floods, and the strong yen.

Mr. Stringer, in a statement, said he wanted Mr. Hirai to take over right away. “He is ready to lead,” Mr. Stringer said, “and the time to make this change is now.”

About Japan Real Time

Japan Real Time is a newsy, concise guide to what works, what doesn’t and why in the one-time poster child for Asian development, as it struggles to keep pace with faster-growing neighbors while competing with Europe for Michelin-rated restaurants. Drawing on the expertise of The Wall Street Journal and Dow Jones Newswires, the site provides an inside track on business, politics and lifestyle in Japan as it comes to terms with being overtaken by China as the world’s second-biggest economy. You can contact the editors at japanrealtime@wsj.com